The present invention relates to robotic surface treatment apparatus. More particularly, the invention relates to intricate guidance of a robotic surface treatment apparatus to traverse paths not previously believed traversable to enable more efficient treatment of corners in a floored area. While the description herein is directed to robotic vacuums, ordinarily skilled artisans will appreciate that the corner guidance aspect of the invention applies more broadly to other types of robotic surface treatment apparatus.
Robotic vacuums clean in their environments by taking various routes through those environments. Rooms in which robotic vacuums operate have various shapes, including corners. Some of these are inside corners, where two walls intersect, as for example in a far end of a room. Some are outside corners, where intersecting walls may form a rectangular or other shape that juts out from a side of the room.
Walls are examples of obstacles that a robotic vacuum will encounter as it traverses a room. Tables, chairs, and other furniture are other examples of obstacles. When a robotic vacuum encounters an obstacle, the robotic vacuum will strike the obstacle, and will either back up, or rotate its wheels or rollers so as to traverse a path around the obstacle. In general, it is desirable to avoid having the robotic vacuum bump into an obstacle, be it a chair leg, a table leg, or a wall. Bumping into obstacles can damage them. Accordingly, robotic vacuums generally are programmed to avoid obstacles when encountered.
In order to detect things like obstacles in and around a room, robotic vacuums need sensors. Some robotic vacuums use what would be termed far-field sensors, to sense contents of a room to be cleaned, identify obstacles to be avoided, and also identify room boundaries, which can include inside corners and outside corners. Robotic vacuums also may use what would be termed near-field sensors, which among other things help in determining when an obstacle is close.
Robotic vacuums have differently-shaped chassis. FIG. 1 shows one such shaped robotic vacuum 100, which may be referred to herein as a “D-shape,” though the essential feature here is that the front portion of the robotic vacuum is substantially flat or straight, rather than curved. The flatness of the front portion of the robotic vacuum yields the advantage that a brush 110 may be positioned more closely toward the front of the device, enabling the robotic vacuum to clean more closely to obstacles around or near which the robotic vacuum is supposed to clean.
The robotic vacuum 100 depicted in this Figure includes a chassis having a front portion 130 and a rear portion 140. The brush 110 is disposed in the front portion 130, and wheels or rollers 120 are disposed in the rear portion 140. The chassis may have a bumper (not specifically shown) which can contract when the robotic vacuum encounters an obstacle. Inside or in proximity to the bumper there may be one or more sensors 160. These may be contact sensors (e.g. sensors which send signals when some portion or all of the bumper is pushed back sufficiently upon encountering an obstacle to create a contact between two opposed portion). These may be non-contact sensors (e.g. optical or ultrasonic sensors which may use ranging to identify the distance from an obstacle). Placement of these sensors on the robotic vacuum 100 can depend on type and purpose.
One or more suitably programmed processors 150 in the robotic vacuum implement various algorithms, stored as program code in inboard or outboard memory 155, to enable the device to traverse a room, and in particular to cover all of the floored area in order to remove dirt, dust, and other debris. The processor(s) also may control robotic vacuum behavior upon encountering an obstacle.
FIG. 2 shows a scenario in which the robotic vacuum 100 is proceeding along a wall, toward a corner. The robotic vacuum needs to be able to turn the corner (in this case, to its left, which is to the right in FIG. 2) and continue to proceed along the wall portion 200. In order for that to happen, in the past the robotic vacuum has pivoted soon enough before encountering the wall portion 200 to be able to avoid the wall portion 200, and then proceed along it.
With damage avoidance in mind, corner traversal has involved guiding the robotic vacuum in an arcuate path from following one wall to following an adjacent wall. FIG. 3 shows an example of such a path, avoiding contact with the adjacent wall. As can be seen from the figure, a relatively sizable swath in the corner remains uncleaned after the robotic vacuum turns the corner.
While traversing inside corners presents one kind of problem, traversing outside corners presents another kind of problem. Unlike inside corners, for which wall detection is relatively straightforward, outside corners involve detection of the absence of a wall, in order for the robotic vacuum to turn to follow the further wall that defines the rest of the corner.
It would be desirable to be able to control the robotic vacuum so that it would recognize inside and outside corners, and in response to that recognition, take a path that enables more complete cleaning of floored areas.